Pyongyang's stated aim is to be able to target the United States mainland and the nation has flaunted the advances in its weapons programme in recent weeks, with the September test of what it said was a miniaturised H-bomb capable of being loaded onto a rocket.

North Korean leader Kim Jong-un inspecting the Command of the Strategic Force of the Korean People's Army.

Tensions have escalated in the wake of North Korea's repeated missile launches and sixth nuclear test on September 3.

Isolated and impoverished, the North says it needs a sturdy nuclear deterrence to protect it from an aggressive USA and the autocratic regime has made militarism a central part of its national ideology.

U.S. President Donald Trump and Kim also hurled insults and accusations of madness at each other earlier this week.

Commenting on the speech, Kim Jong Un said that instead of "making remarks of any persuasive power that can be viewed to be helpful to defusing tension, he made unprecedented rude nonsense one has never heard from any of his predecessors". Finally, they affirmed continued coordination in preparation for President Trump's visit to Japan later this year.

The speech came shortly after the Pentagon announced that US bombers flew a mission over global waters near the east coast of North Korea that went farther north of the Demilitarized Zone than any USA aircraft have this century.

Tillerson said, "The president obviously takes the responsibility of the security of the American people very seriously".

China's Earthquake Administration said the quake was not a nuclear explosion and had the characteristics of a natural tremor. According to the reports, the 3.4-magnitude quake was detected near North Korea's nuclear test site, where previous tests that resulted in earthquakes have been carried out.